1. Field of the Invention
The present invention relates to an apparatus for producing a sound effect in a mobile object depending on the rotational speed of an engine mounted on the mobile object, and more particularly to a mobile object sound effect producing apparatus which is suitable for use on motor vehicles such as passenger automobiles, aircraft such as helicopters, air planes, etc., or watercrafts such as pleasure boats, etc.
2. Description of the Related Art
Heretofore, there have been proposed in the art sound effect producing apparatus for detecting an accelerating or decelerating action made by a passenger (driver) on a mobile object, e.g., a motor vehicle, and producing and radiating a sound effect depending on the acceleration or deceleration through a speaker installed in a vehicle cabin into the vehicle cabin, as disclosed in Japanese Laid-Open Patent Publication Nos. 54-8027 and 4-504916 (PCT).
According to the disclosed sound effect producing apparatus, when the rotational speed of the engine mounted on the motor vehicle increases in response to an accelerating action made by the passenger, a sound effect having a high frequency and a large sound level is generated depending on the increase in the engine rotational speed, and the sound effect is radiated from the speaker into the vehicle cabin to create a staged sound atmosphere in the vehicle cabin.
The vehicle cabin, which serves as a sound field, actually has different acoustic characteristics (also referred to as sound field characteristics, frequency transfer characteristics, or gain characteristics) at different locations therein. For example, there are frequencies that are easier to sense and frequencies that are more difficult to perceive in different passenger positions, e.g., at a driver seat and a rear passenger seat, in the vehicle cabin. It also has been understood that the responses of acoustic characteristics between the speaker position and the passenger position have peaks and dips.
With the conventional sound effect producing apparatus, even if the frequency and sound level of the sound effect radiated from the speaker linearly in proportion to acceleration are increased, since the sound effect as perceived by the ears of the passenger has been processed according to the acoustic characteristics, linearity is lost and some sound effect interruptions tend to occur. Accordingly, the performance level of the conventional sound effect producing apparatus has been somewhat unattractive.